CORINTH, Miss. — The Mississippi man charged with threatening the lives of President Obama, a U.S. senator and a Mississippi judge by mailing them poison-laced letters had grandiose ambitions as an Elvis impersonator, believed that government drones were spying on him and harbored conspiracy theories about black-market trafficking in human body parts, according to court documents and people who know him.

Paul Kevin Curtis, 45, who appeared Thursday in an Oxford, Miss., courtroom wearing shackles and a Johnny Cash T-shirt, has not entered a plea on the charges. His attorney, Christi R. McCoy, said that Curtis “maintains 100 percent that he did not do this.”

“I know Kevin, I know his family,” McCoy said, according to the Associated Press. “This is a huge shock.”

Others who’ve known Curtis were less surprised, however, saying that his long, detailed Internet diatribes and erratic behavior were the signs of a mental illness that he has struggled with for years, one that left him at times delusional, narcissistic, paranoid and dangerously unpredictable when he was not taking his medication.

“When he’s on his medication, he is delightful, charming, likable,” said Jim Waide, a family acquaintance who briefly represented Curtis in a lawsuit a decade ago. “When he’s off his medication, he is paranoid and thinks people are out to get him.”

Curtis’s father, Jack Curtis, 74, said that his son “does have some bipolar issues, but he don’t have a violent streak in him whatsoever. That’s why it’s so hard for us to believe he put ricin in a letter to anybody, let alone the president.”

“He didn’t put no ricin in it, hell, he wouldn’t know where to get it,” said the elder Curtis, adding that his son does write to lawmakers and inherited his father’s outspoken streak.

Curtis allegedly mailed three identical letters laced with the poison ricin on April 8 to the White House, the office of Sen. Roger Wicker (R-Miss.) and a local judge in Tupelo who had once handled an assault case against Curtis.

The letters alluded to Curtis’s novel-in-progress, called “Missing Pieces,” in which he sought to espouse his long-held conspiracy theory about underground trafficking in human body parts.

“No one wanted to listen to me before,” read the letters, according to an FBI affidavit. “There are still ‘Missing Pieces’ Maybe I have your attention now Even if that means someone must die. . . . I am KC and I approve this message.”

In an online profile, Curtis called himself a “Father/Activist/Singer/Songwriter/Business Owner/Rebel.” He described working as a celebrity impersonator along the Mississippi-Tennessee border, often performing as Elvis Presley.

“He was quite entertaining,” Wicker said Thursday, recounting the time a decade ago he hired Curtis to perform as Elvis at an engagement party. “My impression is that since that time, he’s had mental issues and perhaps is not as stable as he was back then.”

Court records show that Curtis has been arrested four times since 2000 in Prentiss County, where he lived most of the past two decades, and where charges against him have included cyber-harassment.

“I’ve been dealing on or off with him, or been made aware of his bizarre behavior, pretty much ever since I became sheriff,” said Prentiss County Sheriff Randy M. Tolar, adding that Curtis sometimes lashed out at him in online forums. “He just seemed to be a very paranoid person.”

David Daniels, a former assistant district attorney, said that he got into a confrontation with Curtis around 2004 at an Elvis impersonator festival in Tupelo, Presley’s birthplace, when Curtis accused him of leering at his ex-wife. After a rehearsal one night, Daniels said that Curtis started beating on the windows of his truck, “screaming and hollering and carrying on.”

“I opened the door to see what in the world is going on and he’s got a long neck beer bottle and started to hit me with it,” said Daniels, who eventually pressed charges against Curtis in a case handled by Lee County Justice Court Judge Sadie Holland, who received one of the poison letters last week. “He stood there and raved for a good 15 minutes and then left.”

In other online posts, Curtis seemed to blame many of his problems, from broken relationships to financial duress, on an episode when he was working as a janitor for a medical center in Tupelo.

According to an extensive post on Ripoffreport.com — which was signed, “I am Kevin Curtis and I approve this message” — Curtis accidentally discovered bags of body parts in the hospital morgue and reported his finding to authorities, who he believed made him a “person of interest where my every move was watched and video-taped.” Curtis described cameras zooming in on him and said he was being followed by security officers.

“He was just devastated because nobody would believe him, nobody,” his father said. “This is the reason he was finally driven to the state of mind that he got in because nobody would believe him. I said son, I believe you, but the thing I want you to try to do as your dad is to forget about it because I can see what it’s doing to you.”

“There was no basis for what he was saying — it was just wild,” said Waide, the lawyer who briefly represented Curtis in 2000 when he sued the medical center for firing him. Waide withdrew from the case once he became convinced that Curtis was mentally ill. “To me it is about mental illness. . . . This family has done everything it can to help him.”

According to court documents filed Thursday, Curtis’s ex-wife reported in 2007 to police in Booneville, Miss., that her husband was “extremely delusional, anti-government, and felt the government was spying on him with drones.”

In a Facebook post apparently authored by Curtis around 2 a.m. Wednesday — some 15 hours before his arrest — he wrote that he was on the “hidden front lines of a secret war.”

“They destroyed my marriage, they distracted my career, they stalked, they trolled, they came into my home, took my computers, had me arrested 22 times and guess what,” he wrote in the post. “I will remain here until Jesus Christ decides it’s time for me to go.”

Curtis was arrested Wednesday evening when he appeared at his home for the first time in two days, said neighbors who were outside and watched.

Latoya Brooks, 32, who lives two doors down, was in her driveway when she said Curtis seemed to speed around the circle toward his home, stop in his driveway and return to his white SUV moments later with a duffel bag.

“All of sudden, they were coming from everywhere, huge trucks; it was scary,” said Brooks. At least three black SUVs bearing U.S. government plates sped from hiding spots through adjacent yards, pinning Curtis’s Ford from the front and the back, the neighbors said.

On Thursday afternoon, behind the home, yellow caution tape crisscrossed the back yard, and near the back door were some of the few items that suggested the one-story brick home was inhabited. A garden hose snaked in looping circles in the grass, and a janitor’s yellow mop pail sat on the narrow concrete stoop.

Aaron Davis covers D.C. government and politics for The Post and wants to hear your story about how D.C. works — or how it doesn’t.

Stephanie McCrummen is a national reporter for The Washington Post. Before that, she was the paper’s East Africa bureau chief. She’s also written about the suburban housing boom and education reform, among other subjects.

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